This invention relates to commutators for electric motors and especially for the provision of a commutator that provides more consistent hot staking of the armature wires to commutator hooks and facilitates easier armature winding with larger diameter wire.
A commutator generally comprises a circular array of electrically conducting commutator bars, spaced from and insulated from one another and provided with commutator hooks for the connection of armature windings in a predetermined winding pattern. In at least one such armature winding pattern using a double flier winder, two wires must be attached to each of two diametrically opposed commutator bars. The commutator bars are generally of equal size and shape so that they subtend equal circumferential arcs; and the hooks are also identical. The wires are permanently attached to the hooks in a hot staking operation in which the heat and pressure supplied must be controlled so that the copper deforms to collapse around the wire but does not melt. The hot staking operation is accomplished by apparatus which stakes all hooks with the same heat and pressure application parameters, but the commutator hooks with two wires require different heat and pressure application parameters for optimum hot staking than those having one wire. Therefore, the parameters of the hot staking process cannot be optimized for either but must be compromised on values that will work for both. In addition, motor designers often wish to use larger diameter wire for the armature windings. The larger diameter wire is more bulky; and two such wires together are not as easily retained on a commutator hook during the winding and hot staking process.